At present, there are two substantially different types of equipment used for retrieving and transporting automotive vehicles which have been wrecked, run off the road, become disabled on the road or in a parking space whether outdoors or in a garage, or have been illegally parked in a towing zone.
In one of these, a tilt-bed truck is maneuvered to a position directly in front of or to the rear of the vehicle which is to be towed, the tilt bed is tilted, ramps are put in place between the rear edge of the tilted bed and the ground in line with the vehicle wheels, and a winch on the truck is used to pull the vehicle up the ramps and onto the bed. The bed is then returned to a horizontal state and the vehicle is shackled in place for transporting. The tilt bed type of automobile recovery vehicle is well-suited for many situations. However, there are others where its use is impractical.
In the other type, which is perhaps more familiar to most people, a truck bed is provided with a derrick having a rearwardly cantilevered boom for a hook apparatus connected by a line to a power-operated winch. Between the hook apparatus and the reelable line usually there is provided a set of parallel straps which tend to wrap partly about the front (or rear) of the automobile as the respective set of wheels is lifted off the ground by reeling in the line and/or by raising the boom. Due to recent changes in the ways that automobiles are constructed, it has become impractical to lift and tow them using this popular and familar type of automobile recovery vehicle.
Chief among the changes are: the change from a mechanical design comprising a chassis mounted to a relatively rigid frame, to a so-called monocoque type of construction, in which no frame is provided; the change from front and rear ends designed to resist deformation to ones designed to absorb mechanical shock to vehicle occupants by crumpling upon impact; the change from the use of steel to the use of aluminum and plastic for the manufacture of front and rear end portions of automobiles; and the decrease in road clearance by the provision of air dams, front and side spoilers and the like.
All of these changes have created the need for a major re-thinking in the ways and means used for lifting and towing automotive vehicles which are in need of being recovered from one site and taken to another.